This invention relates generally to vehicle power systems and, more particularly, to solid state power controls.
Vehicles, such as aircraft, typically utilize one or more power distribution units or power modules to distribute power from a primary power source to various vehicle systems. The solid state power controls in a power distribution unit typically include an electronic switch, such as a FET, and electronic circuitry that provides wiring protection. The FET and circuitry are often referred to as a solid state power controller (“SSPC”). The SSPC has found widespread use because of its desirable status capability, reliability, and packaging density. A typical power distribution unit may include hundreds or thousands of SSPCs.
SSPCs also must operate in the presence of lightning, which can adversely impact electronic devices by causing power surges. Traditionally, aircraft had an aluminum skin that attenuated the lightning current induced on the wires. Some aircraft now use composite materials instead of aluminum for weight and strength benefits. However, composite materials do not provide the same level of attenuation to lightning as aluminum. When lightning hits an aircraft chassis, hundreds of volts may surge between a load in the vehicle system and the aircraft chassis. As such, the lightning requirements of SSPCs have increased.
U.S. patent application Ser. No. 11/491,803 entitled “Method to Increase the Lightning Capability In a Solid-State Power Controller”, now U.S. Pat. No. 7,626,797, describes a method of operating SSPCs in a high-energy lightning environment. This method enables the SSPC to survive a lightning threat and return a load to its defined state once the threat has passed. The method described in this application is suitable for most single-stroke lightning applications and may be suitable for many multiple-stroke lightning applications. However, additional enhancements can be made to prevent repeated potential cycling off and on under an auto-recover mechanism that is part of this prior system during a multiple-stroke lightning application. The discussion with regard to how this occurs from U.S. patent application Ser. No. 11/491,803 is incorporated herein by reference.
There is a need for a simple, relatively inexpensive SSPC with improved lightning protection, that is suitable for exposure to multiple-stroke lightning, that can operate within a lightning environment with minimal system disruption, and that can protect loads from multiple power cycling.